UBC Theses and Dissertations
Spatial and temporal variability of internal wave-driven mixing in the Arctic Ocean Chanona, Melanie
The Arctic Ocean is a unique oceanographic environment that sits at the frontier of the impacts of climate change. In light of the ongoing dramatic changes observed in the Arctic Ocean, there has been a growing interest in improving our understanding of turbulent ocean mixing rates, which play an integral role in setting numerous oceanographic properties. However, scarcity of direct turbulence measurements in the Arctic Ocean inhibits our ability to robustly quantify the space-time variability of mixing in this region and understand the mechanisms that underpin it. This thesis addresses this issue by employing a finescale parameterization of turbulent dissipation to estimate turbulent mixing metrics from three unique Arctic Ocean datasets that span a wide range of distinct space and time scales. Key results include the following. First, estimated internal wave-driven dissipation rates span multiple orders of magnitude, both across large geographic domains and temporally on local scales. Despite this wide variability, dissipation rates display distinct regional differences, with estimated turbulent metrics that are consistently higher on the Canadian Arctic shelf than in the central basins. Dissipation rate time series also vary systematically at key tidal frequencies and on seasonal time scales, but exhibit no interannual trends on periods of up to 16 years. Additionally, a characterization of mixing regimes reveals large-scale spatial structure in the distribution of turbulent, non-turbulent, and marginal mixing regimes. Non-turbulent conditions are most prevalent, but wide variability implies that turbulent mixing occurs in all regions at least some of the time. Finally, dissipation rate estimates from each dataset provide consistent, statistically-significant evidence that tidal forcing and stratification strength modulate turbulence more strongly than wind speed, topographic roughness, or sea ice cover; however, the correlations between each of these metrics and turbulence are generally weak. Overall, the primary contribution of this thesis is the provision of an improved statistical characterization of turbulent metrics in the Arctic Ocean on unprecedented spatial and temporal scales. This characterization puts more limited mixing measurements into a broader context and further provides a valuable observational baseline that can be used to inform Arctic Ocean modelling studies.
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